Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 27)

UniInt Interface User Manual 21
ExDesc
This is the extended descriptor attribute. The extended descriptor is a string attribute. Please
refer to the Historian Tag String Attribute Limits section beginning on page 21 for a
description of the maximum number of characters available to the interface for different
configurations. Typically, if the extended descriptor is used by an interface, it is used to
identify a point, address or location on the data source. If an interface uses the extended
descriptor for this purpose, the interface manual will have a detailed description of the
requirements for this attribute. UniInt uses the extended descriptor to identify Performance
Points (page 26), Trigger Tags (page 22), Failover Control Tags (page 71) and Interface
Health points (page 25).
InstrumentTag
The instrument tag is a string attribute. Please refer to the Historian Tag String Attribute
Limits section beginning on page 21 for a description of the maximum number of characters
available to the interface for different configurations. Typically the instrument tag is used to
identify a point, address or location on the data source. If an interface uses the instrument tag
for this purpose, the interface manual will have a detailed description of the requirements for
this attribute.
DigitalSet
The DigitalSet attribute is used to assign a digital state set to a Historian Point. For standard
usage, refer to Historian Server Reference Guide.
Historian Tag String Attribute Limits
UniInt retrieves three string type attributes from the Historian Server during point loading
other than the point source which is described above. The three attributes are the tag name
(Tag), extended descriptor (ExDesc) and the instrument tag (InstrumentTag). The instrument
tag is not used by UniInt, but the string value for this attribute is sent to the interface during
point loading. The extended descriptor is checked by UniInt for a number of key words that
may identify the point as a UniInt point. The extended descriptor is also passed to the
interface during point loading. The tag name is only used for logging error and debugging
messages. UniInt saves a maximum of 21 characters for the tag name after point loading is
completed. If the tag name is longer than 21 characters, UniInt will save the first ten
characters and the last ten characters of the tag name separated by a tilde (~). If the tag name
length exceeds the number of characters UniInt can retrieve, the last ten characters will be
the last ten UniInt is able to retrieve during point loading. The number of characters UniInt
can retrieve for each attribute depends on the PI API version, the Historian Server version
and whether or not the PI SDK is being used to retrieve point attributes. The following table
describes the number of characters UniInt can retrieve given the configuration. The first
column of the table is ―new API functions‖. The new API functions that support retrieving
the longer attributes are only available if the PI API is version 1.6.x or higher AND the
Historian Server is version 2.x or higher. Please consult the interface documentation to
determine if the interface requires UniInt to load the PI SDK. If the –PISDK startup
parameter is not specified by the interface, the value is 0.